The impact of conflict on infectious disease: a systematic literature review

Background Conflict situations, armed or not, have been associated with emergence and transmission of infectious diseases. This review aims to identify the pathways through which infectious diseases emerge within conflict situations and to outline appropriate infectious disease preparedness and response strategies. Methods A systematic review was performed representing published evidence from January 2000 to October 2023. Ovid Medline and Embase were utilised to obtain literature on infectious diseases in any conflict settings. The systematic review adhered to PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-analysis). No geographical restrictions were imposed. Findings Our review identified 51 studies covering AIDS, Hepatitis B, Tuberculosis, Cholera, Coronavirus 2, Ebola, Poliomyelitis, Malaria, Leishmaniasis, Measles, Diphtheria, Dengue and Acute Bacterial Meningitis within conflict settings in Europe, Middle East, Asia, and Africa since October 2023. Key factors contributing to disease emergence and transmission in conflict situations included population displacement, destruction of vital infrastructure, reduction in functioning healthcare systems and healthcare personnel, disruption of disease control programmes (including reduced surveillance, diagnostic delays, and interrupted vaccinations), reduced access by healthcare providers to populations within areas of active conflict, increased population vulnerability due to limited access to healthcare services, and disruptions in the supply chain of safe water, food, and medication. To mitigate these infectious disease risks reported preparedness and response strategies included both disease-specific intervention strategies as well as broader concepts such as the education of conflict-affected populations through infectious disease awareness programmes, investing in and enabling health care in locations with displaced populations, intensifying immunisation campaigns, and ensuring political commitment and intersectoral collaborations between governments and international organisations. Conclusion Conflict plays a direct and indirect role in the transmission and propagation of infectious diseases. The findings from this review can assist decision-makers in the development of evidence-based preparedness and response strategies for the timely and effective containment of infectious disease outbreaks in conflict zones and amongst conflict-driven displaced populations. Funding European Centre for Disease Prevention and Control under specific contract No. 22 ECD.13,154 within Framework contract ECDC/2019/001 Lot 1B. Supplementary Information The online version contains supplementary material available at 10.1186/s13031-023-00568-z.


Introduction
Military conflicts characterised by war have had a significant impact on healthcare infrastructure and systems [1,2].Affected populations may be subjected to periodic outbreaks of violence (lasting weeks to months), ongoing or recurring insecurity in a protracted conflict (lasting years to decades), or long-term ramifications of previous (usually prolonged) war [1].
In addition, populations in conflict situations present increased incidence of infectious diseases as a result of a multitude of risk factors that precipitate disease emergence and transmission [2].These conflict-related factors include the disruption of vital and health infrastructures and large-scale, forced population movements that further challenge resources in affected countries and aid disease emergence and transmission [1,3].Infectious disease outbreaks in conflict settings present a unique challenge to public health and emergency response.Detection and control of many emerging infectious diseases in conflict situations require a functional healthcare system with a sufficient number of trained healthcare workers and adequate supplies of medications, vaccines, and equipment [1,4].Thus, delays in the detection, response, and containment of an infectious disease outbreak in countries affected by conflict prolong the suffering of the population of the country and elevate the risk of the transmission of infectious diseases to surrounding countries and to countries globally [4].
The Conflict in Ukraine, which started in early 2022 during the COVID-19 pandemic, reminded the world of the risks associated with infectious disease outbreaks among displaced populations and emphasised the significance of having an emergency preparedness plan and response system in place to address infectious disease outbreaks in conflict regions [5].Considering the former, this systematic literature review examines the pathways through which infectious diseases emerge in conflict situations and assesses preparedness and response strategies with the aim of informing the work of public health agencies and countries affected by protracted conflicts.

Methods
The systematic review adhered to PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analysis) presented in Supplementary Table 1 [6].The protocol of this systematic review was pre-reviewed by the European Centre for Disease Prevention and Control.The protocol was not pre-registered in any database for systematic reviews.

Outcomes and inclusion/exclusion criteria
Studies of all study designs, including field reports and perspective articles, with no geographical limitation were considered eligible provided they evaluated infectious diseases in conflict-affected countries and were published in English between January 2000 and October 2023 (Supplementary Table 2).

Study selection
Relevant studies were identified within Ovid Medline and Embase.Subject heading terms and free text words were used to develop a comprehensive search strategy which is presented in Supplementary Table 3.Studies that met the search criteria were evaluated for their validity and reliability.Systematic and non-systematic literature reviews were excluded, but their references were screened.Initially, a pilot round of title/abstract screening was conducted, where a random sample of 100 titles was screened for eligibility independently by two reviewers (ZP, KA) to enable consistency in screening and to identify areas for amendments in the inclusion criteria.A high measure of inter-rater agreement was achieved (percentage agreement > 90%), hence the remaining titles were distributed to be screened independently by two reviewers.For the full-text screening, all full texts were screened for eligibility independently by two reviewers (KN, KA).Any disagreements were discussed with a third reviewer (CV).Documents that passed the inclusion criteria on the fulltext screening were included in the review.

Data extraction, synthesis, and presentation
Data were extracted independently by two reviewers (VM, CV) using a predesigned data extraction sheet.Any discrepancies were discussed and agreed upon.The extracted data were organised in a tabular format and included: study characteristics (first author's name, year of publication), geographical context (country/area), setting, population characteristics, sample size, methodology/study type, and numerical/ descriptive findings regarding type of infectious disease, "conflict-to-infectious disease pathways", and measures implemented and/ or suggested to mitigate outbreaks.A qualitative analysis of the included literature was performed.To evaluate the data and describe each study, a narrative synthesis approach organised by infectious disease category was utilised.

Assessment of study quality
The methodological quality of the included studies was evaluated independently by two reviewers (VM, KA) using the appropriate Joanna Briggs Institute (JBI) standardised critical appraisal tools [7].Any points of uncertainty were addressed through discussion and consensus with a third reviewer (CV).The results of the quality appraisal are presented in Supplementary Table 4.

Results
A total number of 8,042 studies were identified according to the specified selection criteria in Ovid MEDLINE and Embase.After removing duplicates, 7,408 were screened by title and abstract, out of which 355 studies were assessed for full-text eligibility.Through the assessment of the full texts, 304 studies were excluded due to limited data, language and timeframe restrictions, irrelevant outcomes, settings, and study types (reviews, conference abstracts).Consequently, 51 studies were eligible to be included in this current systematic review as depicted in the PRISMA flowchart in Fig. 1.

HIV and HBV
Our systematic review identified five studies reported in Table 1, on Human Immunodeficiency Virus (HIV)/ Hepatitis B virus (HBV) in association with conflict published within the timeframe January 2000-October 2023 [9][10][11][12][13].A higher incidence rate of HIV was reported in the conflict-torn regions of Cote d'Ivoire [9], Libya [10], Ukraine [11], and Uganda [12], as the result of population displacement [9][10][11], continuous interruption of healthcare services [10], overall decrease in healthcare personnel (especially in medical doctors), and reduction in functioning health facilities [9].Additional effects of the armed conflict escalating HIV prevalence in Cote d'Ivoire had been the plundered healthcare delivery structures and the disappearance of laboratory equipment and surveillance data [9].Conflict-affected participants who had experienced abduction and multiple traumas during the war were reported to be at a greater risk of HIV infection [12].It has been noted that human resource and financial constraints, lack of equipment, diagnostic kits for sexually transmitted infections, essential drugs, reduction in the number of condoms sold and the lack of awareness campaigns were major factors impeding the implementation of effective HIV/ Acquired Immunodeficiency Syndrome prevention activities in war-torn areas [9].In Pakistan, the prolonged armed conflict was reported to have caused an increase in poverty, medical deprivation, uncertainty, and a breakdown of social structures that facilitated the transmission of HBV [13].High prevalence of HBV was observed in areas with high frequency of military activities [13].Finally, the low socioeconomic status and the lack of basic health facilities were risk factors associated with HBV infection [13].
With the exception of the Non-Governmental Organisations' (NGOs) active involvement in the prevention of and care for people with HIV in Cote d'Ivoire [9], there was no reported implementation of infection prevention protocols in the included literature.However, preventive measures were suggested and included vaccination [13], awareness campaigns [9,13] with emphasis on age group 15-24 year olds [9], and rehabilitation of health facilities to provide people living with HIV/AIDS antiretroviral treatment and STIs in the long term [9].Furthermore, proactive HIV testing was suggested for internally displaced people (IDPs) and people who frequently travel to war-affected areas to be included in effective preventative measures [11].Also, harm reduction services were suggested as significant preventative measures for HIV outbreaks among people who inject drugs.Finally, the importance of enabling sustainable prevention services and treatment provision in locations where services have been physically disrupted because of the armed conflict was also stressed [11].

Cholera
The current systematic review identified eleven studies, outlined in Table 2, on cholera and conflict published between January 2000 and October 2023 [14][15][16][17][18][19][20][21][22][23][24].In the conflict-affected regions of Monrovia, Liberia [17], cholera transmission was caused most likely by a severe shortage of clean water (as the piped water distribution system was deemed inactive), inadequate sanitation, and overcrowding.The above pathways were compounded by weather conditions as regional flooding washed contaminated water into shallow unprotected wells [17].Due to the conflict in Yemen a massive internal population displacement occurred [18,19,24] and the population had to face insufficient shelter [16], limited access to safe drinking water, shortages of food [14,16,18], poor sanitation, destruction of healthcare facilities [14,16,19,24], disruption in sewage management and wastewater treatment facilities, and a lack of electricity to power water pumps [16,18].Compounding environmental factors (rainfall, flooding, and water contamination) were noted in Yemen as well [14].In Iraq, the armed civil war dispersed a large number of IDPs which, combined with the influx of Syrian refugees into the country (a result of the Syrian civil war), ultimately led to overcrowded shelter arrangements and limited access to drinking water, safe food, and basic healthcare services [15].These factors greatly contributed to the cholera transmission in the region [15].
The war in Syria collapsed infrastructure including healthcare infrastructure, leaving healthcare understaffed and with limited resources [23].This extended to water and sanitation infrastructure forcing the population to rely on unsafe water sources and unmonitored water resources (such as private vendor trucks) and resulted in the rapid spread of cholera [22].Non-operational sewerage systems acerbated by the lack of access to proper water, sanitation, and hygiene (WASH) due to either physical destruction of established water systems or migration into insufficient and crowded camps further exposed residents to waterborne diseases, while the lack of laboratory testing facilities, healthcare personnel and surveillance further facilitate cholera outbreaks [21], aspects which were additionally impacted by the 2023 earthquake [25].
In South Sudan, the large-scale population displacement and movement (both within the country and from neighbouring countries) due to civil war partially explained the differences in the temporal and geographical cholera transmission patterns, together with the synergistic effects of precipitation and climatic determinants that aided bacterial transmission and spread [20].

Implemented:
Not mentioned Suggested: • Enabling sustainable prevention services and treatment provision in locations where services have been physically disrupted.
• Proactive and routine integration of HIV testing for people who have relocated due to the war, or who frequently travel to the war zone.
• Scale-up of harm reduction services for people who inject drugs will be an important factor in preventing new local HIV outbreaks in Ukraine.

Table 1 Impact of conflict on HIV and HBV outbreaks
Overall, response to cholera outbreaks were based on the cooperation of NGOs and governmental healthcare providers [17][18]20] who organised access to safe water through water trucking [21,24], water-sanitation-hygiene (WASH) interventions [15,18,20,22,24], health-hygiene education [16-18, 20, 24], chlorination of public water sources [17,20] case management [20], surveillance through phylogenetic analyses [20], and the provision of oral cholera vaccine (OCV) [20,24].Additional suggestions for optimal cholera control included awareness campaigns [18], distribution of public awareness material on proper personal hygiene, food, and water safety [19], improved preparedness of the public health authorities for surveillance (including public health laboratories at central and regional levels and community surveillance systems) and response systems [19,21,23], preparedness of case definitions [19], rapid testing kits [19], arrangements for leadership and coordination [19,23], and case management procedures [19].Finally, the authors recommended economic development [23], the creation and deployment of stockpiles of medical supplies [19], the OCV global stockpile [16], the development of predictive tools to identify humanitarian emergencies [16], and utilisation of improved methods for measuring population movement within and between countries during complex emergencies [20].

COVID-19
The current review identified six studies published between January 2000 and October 2023 related to COVID-19 in conflict settings [26][27][28][29][30][31], presented in Table 3. COVID-19 outbreaks occurred in the conflictaffected regions of Libya [26,28], Ukraine [27,30,31], and Cameroon [29].The armed civil war in Libya hindered access to populations and thus masked the actual status of the pandemic, particularly in cities devastated by the ongoing conflict where no cases of COVID-19 were reported since no health authority could work there [26].In addition, it caused deterioration of the healthcare infrastructure, inadequate human and financial support, inadequate health facilities with limited bed capacity, lack of readiness for health emergency services, and population mobility due to displacement, all of which were reported as high risk Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) transmission factors in Libya [28].While lockdown measures and isolation procedures within main cities were implemented, the sharing of resources towards the conflict led to inadequate surveillance and response systems [26].In Ukraine, the Russian invasion destroyed the healthcare infrastructure causing severe constraints such as power outages and oxygen shortages [31], damaged primary healthcare facilities [31], and led to mass migrations with people seeking refuge in confined subway systems or relocating to more secure locations [31], factors reported to have impacted SARS-CoV-2 transmission.Furthermore, the war was reported to have adversely affected Ukraine's response to the COVID-19 pandemic through the allocation of resources to warfighting efforts [30], the reduction in medical personnel [27], reduction in hospital beds due to the need for emergency care to war wounded [27], limited testing [27], limited recording of cases in active

Implemented:
Not mentioned Suggested: • Government and opposition groups must be convinced to ease passages of assistance • Importance of cumulative efforts to improve safe water access, sewerage systems, healthcare facilities, nationwide surveillance system, and infrastructure.
• In times of instability and conflict, the expansion of the water supply by private trucks appears to be the only feasible option to meet the population's demands.
• The local population must be encouraged to ensure optimal hygiene by boiling and chlorinating the water, if available.

Table 2 (continued)
conflict areas [27], no medicine delivery due to active hostilities [27], no application of social distancing due to high population density during the evacuation (in trains, stations, shelters) [27], limited application of personal protective measures in shelters [27], and poorly equipped health-care system in occupied territories [30].
The halting of vaccination plans in active conflict areas and the slow vaccination rollout within the other areas of Ukraine were attributed partially to the burden on medical institutions caused by the number of IDPs and the fleeing of medical staff to neighbouring countries [27].
The armed conflict in the Northwest region of Cameroon created destructive conditions that exacerbated the COVID-19 pandemic, including the internal population displacement, the destruction of health facilities, the killing of healthcare workers, the disruption of the regional healthcare system, and difficulties in delivering vaccines in security-compromised areas [29].
The reported emergency control measures included social distancing, face masks, hand washing, isolation, limited movement and travelling, acquisition of diagnostic test kits for COVID-19 detection at checkpoints across state borders, self-isolation of troops, and the deployment of mobile hospitals and military medical centres for COVID-19 prevention and treatment [30].In addition, immediate financing was provided to the Institute of Molecular Biology and Genetics of the National Academy of Sciences of Ukraine for the production of self-tests [30].
Suggestions for mitigating SARS-CoV-2 transmission included enforcing national policies with internationally accepted guidelines and tools adapted to conflict situations [26] and rebuilding healthcare systems [31].It was further suggested that NGOs, doctors and front-line workers should extend their support by supplying vaccines and medicine and that standard medical facilities should be prepared with medications, equipment, medical military personnel, and a combat support hospital with intensive care capacity [31].Other suggested preparedness strategies included training of health facility • The armed conflict resulted in a destroyed and understaffed healthcare system with limited resources and lack of coordinated response, as well as population displacement

Implemented:
Not mentioned Suggested: • The provision of safe water and improved sanitation and hygiene practices must be urgently implemented to prevent further spread of the disease and reduce preventable deaths • improve the testing and reporting capacity of the health system and strengthen the surveillance systems to detect and respond to outbreaks promptly • Coordinated efforts and collaboration between local health authorities and international organisations working in Syria are important.
• International organisations should provide technical and financial support to strengthen the country's response, including training and equipping healthcare workers, improving disease surveillance, and expanding access to testing and treatment.
• Effective community engagement is critical for the success of any disease prevention and control program, particularly in conflict-affected settings where trust in government and healthcare systems may be low • Economic development and universal access to sustainable safe drinking water and adequate sanitation, including the improvement of environmental conditions, the rehabilitation of damaged health facilities, and the improvement of early warning systems should be prioritised • The main priority must be rebuilding the country's health system and increasing access to safe drinking water and sanitation facilities, particularly in conflict-affected areas    [26,28], disease awareness programmes for civilians [26,28,31] and for military personnel [31], establishment of isolation spaces [28], and the scale-up of COVID-19 vaccination [29].It was additionally suggested that surveillance and testing policies should not be restricted to severely hospitalized patients but should include milder cases and asymptomatic infections and that access to accurate rapid tests should be broad [30].The allocation of resources, beds, and medical staff was recommended to be on strict prioritization [30].Finally, information • The medical readiness system in Ukraine will need to create reserves of medical equipment, medicines, medical devices, personal protective equipment, disinfectants, and capacity building and training • Surveillance and testing policies not only for severe cases but should include milder cases and asymptomatic infections • Broad access to accurate testing • International coordination, knowledge and information sharing between states/ international partners for rapid implementation of containment, mitigation, treatment, and rapid vaccine rollout options • Step up capacity building efforts to train and supply Ukrainian epidemiologists and laboratories to handle the diagnostic and biostatistics requirements for responding to any infectious disease outbreak and integration biosurveillance, antimicrobial resistance • Strict prioritisation in allocation of resources, beds, and medical staff • Interoperability with international partners must be increased and expanded upon across all domains of battle and disaster response  sharing of data and interoperability with international partners was stressed [30].
Delay in the diagnosis of TB patients and self-treatment prior to diagnosis have been associated with increased transmission and morbidity [32].The armed conflicts in Ethiopia disrupted the healthcare system and economic resources were diverted to priorities other than health needs, this meant that patients were unable to seek prompt TB care resulting in diagnostic delay and hampered TB control efforts [32].In South Sudan, key challenges resulting from civil unrest that contributed to TB transmission included the limited number of healthcare providers, the interruption of treatments because travel was impossible, and the relocation of people [34].During the war in Ukraine and Russia, internal displacement of citizens resulted in the dispersal of drug-resistant Mycobacterium tuberculosis to affected and neighbouring countries.The heightened risk of interrupted treatment during war contributes to an increased likelihood of drug resistance and treatment failure [35].In addition, the war resulted in a large population movement fleeing Ukraine to reach France among which TB cases and consequently the spread of the TB [36] Finally, Adamawa State experienced several years of violence with severe disruption of public health activities including TB services and a massive population displacement [33].The study shows that years and places of higher conflict were associated with lower TB notifications [33].The decrease reflects the displacement of the populations to other locations that were considered safer, the limited or no access to TB health services due to displacement, the general disruption of TB services along with the reduced number of healthcare staff [33].
Suggested measures for TB control in conflict zones were the expansion of user-friendly directly observed short-course treatment (DOTS), the establishment of early TB detection training programmes for community health workers [32], and population-target risk communication activities [33].Importantly, international organisations providing health services should be given unconditional access to conflict zones [32] while the global health community should be ready to step up efforts to detect and treat drug-resistant and drug-susceptible TB, as well as to strengthen screening initiatives for TB prevention and treatment in migrants and close contacts [35].Finally, it was noted that a pre-established well-organised network of TB centres such as the CLAT network is effective in the case of sudden mass migration from a high TB incidence country [36].

Ebola virus disease
The current systematic review identified five studies on Ebola virus disease and conflict published between January 2000 and October 2023 [37][38][39][40] (Table 5).The Ebola epidemic in the Democratic Republic of Congo (DRC) [37−40] occurred in the midst of an active armed conflict, geopolitical volatility and with a million displaced people [31].The conflict in the region was associated with inhibited case detection [39,40], delayed reporting of the outbreak [37,40], delayed time to isolation [40], deteriorating security [39], dampened vaccine deployment [40], and limited follow-up [40] especially with people in the zone of violence [37] all of which led to an increase in transmission that was attributable primarily to the organised attacks by armed groups targeting healthcare providers and Ebola treatment centres [39,40] and the population's increasing distrust of the response effort [38][39][40] that impedes information-sharing and cooperation.
In response, the DRC Ministry of Health collaborated with health workers from NGOs and UN agencies and, alongside with the linguistic and cultural awareness of local personnel, implemented contact tracing [38], medical isolation [38], exploratory therapies [38], ring vaccination [37−39], entry and exit screenings at key points [39], real-time epidemiologic surveillance of contacts [39], provision of safe and dignified burials [39], and medical treatment [39].Additional measures that aided the outbreak's containment were the rapid decontamination of facilities with identified cases and the distribution of infection prevention and control equipment to healthcare facilities and strategic areas (schools, public offices, and transition points) [39].
Suggested preparation strategies included engaging the community to build trust among residents [38][39][40], ensuring the safety of frontline workers that provide treatment, conducting contact tracing, and distributing vaccines [38][39][40].In addition, the significance of increased security and expanded capabilities in laboratories, surveillance, data analysis, and clinical response were emphasised [38].Finally, the necessity of a transparent framework for responding to epidemics in conflict zones was acknowledged, which should be supported by national action plans to safeguard public health action in conflict zones [38].

Poliomyelitis
The current review identified five studies published between January 2000 and October 2023 on poliomyelitis and conflict [41][42][43][44][45] presented in Table 6.According to a study that collected data from countries affected by conflict and experiencing polio outbreaks between 2011 and 2014, polio was more common in countries with political conflict and instability [42].People faced a lack of access to clean water, as well as deteriorating sanitation and living conditions as a result of conflict and political instability, which aided polio transmission significantly [42].Furthermore, polio incidence was found to be spatially associated with violence [as represented by the location of Improvised Explosive Devices (IEDs)] in Afghanistan [44].The high-risk districts had a statistically significant greater mean number of IEDs compared to non-polio high-risk districts [44].According to the authors, violence in the region leads to reduced rates of polio vaccination and disruption in vaccine coverage, which in turn is responsible for increased polio incidence [44].It was reported that vaccination campaign workers and public health workers had been directly targeted by armed groups, with abductions and murders.The Afghani government and international agencies had been forced to suspend operations or delay subnational immunisation days in some regions.The response was challenged from the combined impact of a government transition, a depressed economy, droughts, floods, food insecurity, displacement, and severe gaps in delivery of health services [45].
In Syria, poliomyelitis reappeared in mid-2013 during the civil war [43].Reported conflict-to-disease related factors included the collapse of the healthcare system and infrastructure, decline in the economy, and shortages of food, water, and inadequate sanitation [43].The emigration of healthcare personnel from both government and nongovernment territory due to conflict further affected the country's healthcare system [43].Moreover, a severe lack of basic medications and preventative services had ensued, including a sharp decline in the overall vaccination coverage to only 50% in 2015 [43].Finally, in Iraq children who had been exposed to war were over 20% points less likely to receive neonatal polio immunisation compared to children who had not been exposed [41].According to the authors, the decline is part of a broader war-induced deterioration of routine maternal and newborn health services [41].
In response, the World Health Organization (WHO) mandated polio immunisation for all travellers to and from Pakistan, Syria, and Cameroon and suggested travel vaccinations for Afghanistan, Nigeria, and other nations as a preventive measure [42].Additionally, the Global Polio Eradication Initiative (GPEI), which coordinated the actions of the Afghan government, UNICEF,

Author Country, Setting, Timeframe Population Conflict to Disease Pathways Prevention and Preparedness Strategies Suggested/Implemented
Dahl et al., 2022 [35] Ukraine and Russia

Population of Ukraine and Russia
• The internal displacement of citizens, especially within Ukraine but also in Russia, and migration of war refugees has large consequences including the dispersal of drug-resistant Mycobacterium tuberculosis in both the affected and neighbouring countries, which are presently facing an un-precedented flow of refugees.
• Initiating and maintaining a course of anti-TB therapy during war, or during migration, is undoubtedly also associated with a higher risk of inappropriate or interrupted treatment and, followingly, an increased likelihood of drug-resistance, treatment failure and death.

Implemented:
Not mentioned Suggested: The international health community must be prepared to intensify the capacity of detection and treatment of both drugsusceptible and drug-resistant TB, and to strengthen screening programmes for TB prevention and treatment of active disease among migrants and close contacts of people with TB, ultimately to diminish the impact of the ongoing conflict and its future consequences for global health.Guthmann et al., 2023 [36] Ukraine and France 2022-2023

Population of France
• The spread of TB due to the war and the large population movement fleeing Ukraine to reach France among which TB cases

Implemented:
Active CXR screening to detect TB cases among the displaced population Suggested: Pre-established well-organised network of TB centres such as the CLAT network in case of sudden mass migration from a high TB incidence country.Increasing effectiveness of the existing strategy may require further well-trained man-power and financial support, both likely not being readily available.and NGOs, represented a significant polio mitigation effort through which vaccination sites, vaccinators, and supplemental immunisation activities were organised, and "mop-ups" (i.e.revaccination of children close to a polio outbreak) were carried out [44].Moreover, in 2020 the GPEI authorised the use of trivalent OPV (tOPV) for outbreak response, with supplementary immunization activities carried out throughout 2021 and 2022 outbreak response [45].In 2022 the program reached 3.5-4.5 million children that were previously unreachable because the insurgency prevented access [45].The development of Acute Flaccid Paralysis took place and also environmental surveillance with the systematic sampling and virologic testing of sewage sites [45].Finally, genomic sequence analyses were preformed to assess cross border transmission between Afghanistan and Pakistan [45].Regarding Syria, Syrian and regional NGOs, in an effort to control the outbreak, established vaccination   • Violence leads to reduced rates of polio vaccination, which is, in turn, responsible for increased polio incidence • Vaccination campaign staff and public health staff were being directly targeted by armed groups, with abductions and murders • Conflict creates a lack of public trust in the governmental and international organisations that run vaccination campaigns.Without trust, a successful vaccination programme is difficult • Violence can damage infrastructure, cause suspension of vaccination activities, and influence the behaviour of whole communities

Implemented:
The GPEI, a project of the WHO, coordinated the efforts of the Afghani government, UNICEF, and various NGOs to eradicate polio.The GPEI national team was responsible for policy, planning, and vaccine supply, while provincial teams were responsible for implementation, supervision, and monitoring of programme activities: • Organised 1,251 vaccination sites and over 2,700 vaccinators were organised to provide routine services • Organised supplemental immunisation activities including national and subnational immunisation days • Conducted "mop-ups:" children in the vicinity of a polio outbreak were revaccinated Suggested: • Support polio vaccine distribution efforts in communities exposed to violence • Take all available measures to avoid entangling the polio vaccination campaign in political dynamics of the armed conflict • Direct negotiation to convince anti-government groups to allow safe passage of health staff through opposition-controlled regions Table 6 Impact of conflict on Poliomyelitis outbreaks facilities, trained local personnel, and delivered vaccines to children in areas inaccessible to WHO [43].
The control of polio and other infections in impoverished, conflict-ridden areas was suggested that may be improved by providing displaced families and those in high-risk areas with urgent care in the form of clean water, increased nutritional measures, improved sanitation, and easy access to health care and vaccinations [42].Additionally, Geographic Information System (GIS) maps presenting the recent virus origin and the current virus movement may help to identify areas with high rates of polio and to predict the possibility of movement of the virus to neighbouring countries, thus guiding preventative measures [42].Furthermore, the lack of poliolicenced laboratories or the lack of access to laboratories in conflict zones was noted, necessitating international surveillance to be strengthened [43].Finally, financial and logistical international support for vaccine and immunisation of the population in conflict-torn countries is needed [43].The authors emphasised that during conflicts, WHO, UNICEF, and UN agencies involved in global health should be supported, funded and allowed   to function independently of governments to provide necessary medical and humanitarian relief for civilians [43].Also, in order to ensure uninterrupted immunisation coverage and thus successful eradication of polio in conflict zones, direct negotiations with anti-government organisations should be conducted [44].

Malaria
The current review identified two articles on malaria prevalence in conflict-affected areas of Timor-Leste and Sub-Saharan Africa that were published between January 2000 and October 2023 [46,47], presented in Table 7.
During the 2006 Timor crisis, gang fights and street violence ensued, over 3,000 homes burned down mostly in the capital city, Dili and 15% of the country's population was displaced [46].The IDPs sought refuge in camps, churches, convents and schools, with some displaced from Dili, to districts [46].In Dili, more than 60 camps were established to provide temporary shelter for displaced people [46].Breakdown of health services and of malaria control programmes, movement of people from low to high transmission areas, and environmental deterioration encouraging vector breeding, such as rainy seasons are factors that contribute to the increase of morbidity and mortality due to malaria [46].The authors argue that the timing of the crisis which occurred at the end of the rainy season along with the early malaria interventions which covered treatment, massive insecticidetreated nets [48] distribution with emphasis to pregnant women and children under five, vector control, surveillance and health promotion for IDPs possibly prevented major Malaria outbreaks in the area [46].It was recommended that future malaria intervention responses be planned beyond the IDP camps and adequate resources and expertise be made available to ensure a whole-city approach [46].The second study examined the link between conflicts and variations in the Plasmodium falciparum parasite in Sub-Saharan African countries from 1997 to 2010, during which a significant number of armed conflicts occurred [47].The duration of conflicts, the distance from conflicts, the number of conflicts, and the level of violence associated with the conflicts were found to be major factors that explained the prevalence of malaria [47].More specifically, locations affected by a larger number of longer and closer conflicts with significant amounts of violence and deaths were more likely to see an increase in P. falciparum prevalence [47].Moreover, decreased post-conflict P. falciparum parasite rate was associated with conflicts without violence against civilians, without violent transfer of territory or battles with change of territory, and without riots/protests [47].The maintenance of intervention coverage and provision of healthcare in conflict situations to protect vulnerable populations was suggested [47].

Leishmaniasis
This systematic review identified two studies on leishmaniasis displayed in Table 7 [49,50].Leishmaniasis outbreaks occurred in the conflict-affected regions of Lebanon [49] and Syria [50].The outbreak in Lebanon was reported to be a result of the Syrian crisis and the consequent influx of Syrian refugees [49].The massive and rapid increase in the arrival of Syrian refugees, and their large-scale movement to different regions of Lebanon, without allocation to designated camps, along with the limited access to treatment and the absence of welltrained personnel exacerbated the spread of the parasite [49].The Lebanese Ministry of Public Health (LMOPH) to contain the spread of infection implemented the following measures: sprayed pesticides to kill the vector, provided free treatment and diagnosis for emerging cases, distributed free medications to the different primary care centres, and monitored the disease activity [49].Additionally, medical and healthcare professionals received training on disease symptoms, and the Lebanese people and Syrian refugees received education on disease symptoms and medical treatment [49].Furthermore, the government established new Leishmania detection and treatment units in all Lebanese hospitals, mainly in rural areas and near refugee camps [49].The authors note that the measures taken by the LMOPH are key to any health emergency response, but require the cooperation of other concerned parties to ensure success [49].The importance of coordinating efforts among various governmental departments, international agencies, local authorities, medical associations, and NGOs for containing similar outbreaks in Lebanon, or any other country in the region is emphasised [49].
In Syria, the conflict displaced more than 6.5 million people causing a major refugee crisis, severely damaged 60% of Syrian hospitals, and greatly reduced the pharmaceutical production capacity of the country [50].The destruction of healthcare infrastructure, the over-crowding of what was considered "safer Syrian cities" (such as Latakia) and their healthcare facilities, and the displacement of a large population from leishmaniasis-endemic areas enabled the transmission of the Leishmania parasite [50].To control transmission, healthcare authorities initiated a campaign that consisted of vector control, early detection and treatment, and public education.Improving the living circumstances in sites with high population densities, enforcing better health-care services, and activating surveillance, early diagnosis, vector control, and public education is suggested as an integral part of any plan to successfully control and eliminate leishmaniasis [50].

Implemented:
The LMOPH to contain the spread of infection: • sprayed pesticides to kill the vector • provided free treatment and diagnosis for emerging cases, • distributed medications free of charge to the different primary care centres, • monitored of disease activity, • trained physicians and health care workers on disease symptoms, raising their index of suspicion, • educated the Lebanese public and Syrian refugees about the disease symptoms and how to seek medical advice and treatment.
• assigned new centres for Leishmania detection and treatment in all Lebanese hospitals, including those in rural areas and near refugee camps.

Suggested:
The coordinated efforts and cooperation among governmental departments, international agencies, local authorities, medical associations, and NGOs are critical for containing any outbreak.Youssef et al., 2019 [50] Latakia city, Syria, 2008-2016

Population of Latakia city Leishmaniasis
The 2011 Syrian conflict: • Displaced more than 6.5 million people • Devastated the Syrian healthcare infrastructures, severely damaging 60% of the Syrian hospitals, and greatly reducing the pharmaceutical production capacity of the country.
• Crowding of the "safer Syrian cities" and their healthcare facilities, and displacement of a large population from leishmaniasis-endemic areas • Potentially exposed younger males enrolled in the army who would transfer the parasite.

Implemented:
The LMOPH initiated a control campaign following the 2013 outbreak in the Lebanese refugee camps that included:  • The majority of the LGAs were not fully accessible for optimal conduct of the measles immunisation campaign • Children in inaccessible areas were denied access to immunisation services.
• Inability to implement RES strategy to deliver measles vaccine to partially accessible areas because of escalation in insurgency during the time frame and the prioritisation of the military and joint task forces on addressing the security risk over delivering health commodities • Aggravation of factors related to disease transmission like the mass movement of people between IDP camps and host communities which may introduce transmission of measles

Implemented:
Organised vaccination campaigns based on the accessibility mapping of each area developed by the government and partners.The immunisation strategies included: • Fixed posts (where the team was based at the health facilities) and temporary posts (located at strategic areas of the communities such as schools, markets, places of worship etc.).• The RES strategy which was implemented in some partially accessible parts of the State involved the deployment of vaccination teams with security cover by the Military or armed local vigilante referred to as the Civilian Joint Taskforce • Combined Human and Animal Vaccinations teams were organised targeting nomadic populations.

Suggested:
• The strategy of Reaching Inaccessible Children was adopted to reach eligible children in security-compromised areas by leveraging the military personnel to conduct vaccination, but the plan was suspended and, thus, not implemented.
• The engagement with the military must continue and be strengthened to ensure increased collaboration with security forces

Measles
Two studies were identified on measles and conflict between January 2000 and October 2023 [51,52] (Table 7).Higher incidence rates of measles were reported in conflict-affected Darfur, Sudan [51] and in Borno state, Nigeria [52].In 2003, Darfur experienced civil conflict that resulted in the internal displacement of approximately one million residents and an estimated 170,000 persons fleeing to neighbouring Chad [51].The conflict left a vulnerable population with limited access to food, health care, and other basic necessities, which adversely affected measles vaccination coverage [51].During March-April 2004 a measles outbreak among IPDs was reported in Darfur [51].In response, the Federal Ministry of Health in collaboration with the UNs and NGOs conducted vaccination campaigns targeting children aged 9 months -5 years to limit the transmission.Moreover, clinics were established in IDP camps to vaccinate current and incoming residents [51].Despite these measures, measles virus transmission continued to occur both within the camps and in neighbouring communities [51].Vaccination was organised using a combination of fixed posts and outreach immunisation teams, the use of checklists to monitor vaccination sessions, social mobilisation activities, and surveillance for adverse events after vaccination.In addition, rapid convenience surveys were used to monitor coverage in hard-to-reach areas [51].Tally sheets were used to monitor campaign coverage, and data were sent to the federal level for compilation and analysis [51].
In Borno state, Measles vaccination campaigns were organised based on accessibility mapping of each area [52].They organised both fixed locations of the healthcare team at health facilities and temporary locations at strategic areas of the communities (schools, markets, and places of worship) [52].In addition, the Reaching Every Settlement (RES) strategy was implemented in some partially accessible areas and involved vaccination teams with security cover by the Military or armed local vigilante referred to as the Civilian Joint Taskforce [52].For nomadic populations, combined Human and Animal Vaccination teams were organised [52].Finally, the strategy of reaching Inaccessible Children was adopted to reach eligible children in security-compromised areas by leveraging the military personnel to conduct vaccination, but the plan was suspended by the military [52].Although the above immunisation strategies were organised, the escalation in insurgency during the timeframe and the prioritisation of the military to address security issues over delivering health commodities compromised the vaccination campaign [52].Most of the local government areas (LGAs) were not fully accessible and   children remained trapped with no access to immunisation services [52].Another reported factor related to the introduction and transmission of measles was the mass movement of people between IDP camps and host communities [52].The authors recommended a continuous, stronger engagement with the military, re-establishment of holding camps, vaccination posts at all entry points into IDP camps and host communities to ensure screening and vaccination of new entrants [52].

Dengue
Our systematic review identified one study reporting on the dengue outbreak in Taiz, Yemen in 2016 during the civil war [53](Table 7).According to the authors, the prevalence of dengue in Taiz increased markedly because of the ongoing civil war which damaged the public health infrastructure of the country [53].More than 2.2 million people were displaced and moved into overcrowded shelters forced to live in unsanitary conditions with limited access to medical care [53].The war led to the creation of numerous potential mosquito-breeding sites such as open water storage containers, areas with inadequate drainage, discarded plastic containers in which water accumulates, and puddles of water and resulted in propagation and transmission of the mosquito-borne dengue virus that was difficult to control [53].No prevention or preparedness strategies were noted within this report.

Diphtheria
Our review identified one study that investigated a diphtheria outbreak in Bangladesh among Myanmar nationals displaced due to political conflict [54].As noted in Table 7, from August to December 2017, a massive influx of approximately 630,000 forcibly displaced Myanmar nationals created makeshift settlements in and around established refugee camps in Bangladesh where the first suspected diphtheria case was reported which resulted in over 800 suspected cases reported in the area by mid-December.No prevention or preparedness strategies were noted within this report [54].

Acute bacterial meningitis (ABM)
Our review identified one study that assessed ABM outbreaks in Yemen before and during the civil war [55].The study noted that the civil war reduced vaccination coverage and increased the prevalence of suspected cases, with areas which were more affected by civil war found to have the highest suspected prevalence and lowest vaccination coverage [55].Overall, the ongoing war and the land-sea-air embargo imposed on Yemen eventually caused the vaccination coverage rate to decline [55].

Studies assessing the impact of conflict on multiple infectious diseases
The current review identified and analysed six studies on multiple infectious diseases published between January 2000 and October 2023 [56][57][58][59][60][61] (Table 8).Higher incidence rates of several infectious diseases were reported in Iraq [56], in the Southwest region of Cameroon [57], in Syria and neighbouring countries [61], in Jordan [59], in Ukraine [58], and in DRC [60].During the peak years of the war in Iraq, particularly during the US military surge (2007)(2008)(2009), the incidence of infectious diseases increased significantly [56].Iraq experienced four vaccine-preventable disease outbreaks: measles in 2009, mumps in 2004 and 2016, and rubella in 2004.These outbreaks were reported to have been attributed to deterioration of the infrastructure during the conflict, lower vaccine coverage and higher vaccine failure due to inappropriate vaccine handling, failure to maintain the cold chain, and improper administrative procedures [56].The Cholera outbreak in 2008 was reported to have been facilitated by the war-related deterioration of water quality and sanitation.The rise in the incidence of Hepatitis A was attributed to conflict zone-related circumstances, namely poor primary hygiene practices, interrupted water supplies, and population displacement [56].In response, the Ministry of Health reoriented public health sector towards primary care, restored disease surveillance systems and screening programmes, and initiated individual smart cards with health records and messages for required immunisations and clinic visits [56].The importance of vaccination along with immediate water treatment and case management for the successful control of cholera outbreaks was also mentioned [56].
In the Southwest region of Cameroon, the reduction in healthcare utilisation due to reduced community accessibility to health facilities was a main consequence of the armed conflict [57].The conflict led to the abandonment of healthcare facilities because of the attacks on health personnel and infrastructure.Moreover, there was disruption to drug deliveries to health facilities, roads were blocked, communication networks were destroyed, and the disease surveillance system was disrupted due to active fighting [57].The disruption of normal life and health services due to the insurgency created an enabling environment for the spread of infectious diseases [57].In response, vaccine rollouts were targeted towards displaced children and community health workers were engaged to provide a continuity of care.It was suggested that local, national, regional, and global authorities should work together to develop risk-mitigating interventions in settings with armed conflicts to preserve the delivery and utilisation of health services [57].
In Syria and neighbouring countries, the number of vector-borne disease outbreaks reported among human

Children under-five living in Jordan
• A massive influx of Syrian refugees in Jordan placed immense pressure on the country's over-stretched resources and affected the country's health care system with exerted demand.
• People coming through conflict-driven displacement had no or low access to healthcare and lack basic healthcare facilities.
• Conflict-driven displacement has an immediate effect on child health because of access, availability and affordability issues with regard to health care services.

Implemented:
• Given the large number of refugees in urban areas, sanitation programmes and sewage networks have been implemented among refugee concentrated camps Suggested: • Concerted action is required to safeguard the health needs and avert public health emergencies due to conflict driven displacement.
• Coordinated and effective measures are needed to provide the best health care services among the displaced populations to prevent health risks.
• Collaborative efforts through global partners can help the countries facing the challenges of managing these health care emergencies Table 8 Impact of conflict on Multiple Infectious Diseases outbreaks and animal populations increased significantly following the onset of conflict in Syria [61].Conflict-related factors that led to the spread of infectious diseases were the disruption of WASH infrastructure and standard health services, migration, and overcrowded healthcare systems not equipped to handle a surge of forcibly displaced people [61].
In Jordan, the Syrian conflict led to the influx of Syrian refugees that placed further pressure on the country's over-stretched resources [59].People arriving as a result of conflict-driven displacement had no or low access to healthcare and thus were at a greater risk of exposure to diseases [59].Additionally, conflict-driven displacement was reported to have an immediate effect on child health due to disrupting access, and limited availability and affordability of healthcare services [59].In response, sanitation programmes and sewage networks were organised in refugee camps [59].Coordinated and effective measures to provide the health care services among the displaced populations and collaborated efforts with global partners in managing health care emergencies were suggested [59].
In Ukraine, the Russian aggression resulted in the destruction of healthcare facilities [58].In areas with active hostilities, critical supplies, including oxygen, insulin, and medicines were in short supply, their delivery was disrupted, and people were displaced into overcrowded shelters with limited or no access to water and sanitation facilities [58].As a result, a reported increase in cases of HIV/AIDS, TB, and COVID-19 was observed [58].The authors suggested that Ukraine's infrastructure and essential systems should be rebuilt to ensure appropriate  recovery for the country and its people and surveillance and support should be strengthened [58].
In DRC, the conflict rendered certain health zones inaccessible, increased population/contact mobility, reduced aid for basic services, and impacted response activities [60].The aforementioned factors, in addition to the pre-existing community mistrust and high population density, led to increased EVD transmission [60].The authors proposed that the strategies and response measures implemented for Ebola be used for the mitigation of COVID-19 in DRC including the transfer of protocols and (Table 8) [60].

Discussion
Conflict within or between countries adversely affects population health.The studies reported here demonstrate that in conflict circumstances, affected populations are at an increased risk of infectious disease outbreaks.Infectious diseases have a significant impact on the population's health, thus understanding the link between conflict and infectious diseases is essential.With the current systematic review, we outlined the types of infectious diseases that have been emerging in conflict-affected countries, the pathways leading from conflict to infectious disease outbreaks, and noted the prevention or response strategies and protocols implemented and recommended to prevent and control infectious disease risks.
More specifically, infectious diseases are more likely to be introduced and transmitted during conflict situations as there are often large-scale population movements of IDPs [9-11, 15, 24, 18, 20, 27, 28, 29, 34, 33, 46, 50, 51, 56, 57, 58] and large influxes of refugees to neighbouring countries [15,49,57,59,62] which challenge resources in countries and result in overcrowded settings, poor hygienic conditions, broken infrastructure, and lack of and difficulty in receiving medical treatment [3].These factors may also have an impact on countries not directly involved in the conflict [3].Forcibly displaced populations are affected by a wide range of infectious disease pathogens mostly due to infections acquired in the destination country, cited as related to interrupted vaccination and a breakdown in local health infrastructure and mistrust of local medical care [63].These findings are consistent with prior studies that have demonstrated low risks of imported acute infectious diseases impacting host country epidemiology while crowding associated with temporary resettlement increases the risk of outbreaks among displaced residents [63].More specifically, conflicts and wars led to forced large-scale population migration, large numbers of IPDs, and influx of refugees which in turn led to high population density and large numbers of people that moved into overcrowded shelter arrangements with limited access to sanitation facilities, safe water and limited or no access to medical care.Another factor related to the introduction and transmission of infectious diseases was the mass movement of people between IDP camps and host communities [52].Additionally, internal population displacement was associated with the geographic spread of infectious diseases from the regions involved in the armed conflict to the rest of the country and to neighbouring countries (such as between Ukraine and Poland) [64] with phylodynamic evidence supporting this case [65,66].High population density during evacuation plans [27] and the lack of social distancing among militaries and prisoners [43,67], were also reported as pathways leading to the transmission of infectious diseases.
Conflicts have been noted as a direct cause of the destruction of electricity, water, transportation, and health infrastructure as well as the disruption in functioning health systems [27,28,31,42,43,50,53,[56][57][58].Organised attacks on power, water, and transportation infrastructure were reported across studies.In areas with active hostilities, roads were blocked and destroyed, highways were attacked, communication networks were broken [57,58], power failures/loss of electrical power occurred [16,31], clean water sources were disrupted, and critical medical products, including vaccines, were in short supply with their deliveries to health facilities disrupted [27,29,57,58,60].Furthermore, organised attacks on health infrastructure, including the bombing of hospitals, factories and dispensaries as well as the targeting and persecution of healthcare personnel resulted in the destruction and abandonment of healthcare facilities [39,40,43,57], a significant reduction in medical personnel, and ultimately the disruption of disease surveillance systems [9,26,56,57] and of the necessary healthcare services.Surveillance systems are often weak in conflict situations, resulting in delays in the detection and reporting of epidemics [37,40].Armed conflicts also were reported to have caused treatment interruptions [9-11, 34, 35, 46], limited patient-provider consultations [57] and limited follow-up [40], especially for people in areas with active hostilities.Other factors that aided transmission of water-borne infectious diseases were reported and these included disruptions in sewage management and wastewater treatment facilities as well as inactive pipe water distribution systems that resulted in severe shortages of clean water [16,17,56].
Additionally, certain war zones were rendered inaccessible to governmental organisations and NGOs due to active fighting or because they were controlled by antigovernment organisations.In these areas, the population could not be reached, medicine could not be delivered or delivered in time, administration of vaccinations was interrupted [58,61,63], and access to treatment was limited [34,35,60].The lack of vaccination plans in active conflict areas was also noted [27].
Finally, conflicts may fuel epidemics by increasing population vulnerabilities due to poverty, malnutrition, medical deprivation, uncertainty, and a breakdown of social structures.Shortages of food, drinking water, and medication were important conflict-to-disease-related factors in the studied literature.Conflicts make populations vulnerable and insecure with limited access to safe water, food, healthcare, and other basic necessities [9, 13-20, 24, 27, 37, 42, 43, 56, 58].Moreover, migrants are often emotionally and physically stressed and thus have low immunity to disease endemics in the new area [35].Children are the most vulnerable group as malnutrition, lack of basic necessities, and limited access to healthcare make them more susceptible to infectious diseases if neither vaccinated nor previously exposed [45,52,59].In addition, increasing community distrust of the government and the public health response was reported in some of the affected countries [38-40, 42, 44, 60].Public mistrust in the governmental and international organisations that run vaccination campaigns resulted in increased rates of unvaccinated adults and children with low immunity to vaccine-preventable diseases [44], impeding the control of vaccine-preventable infectious disease outbreaks.Finally, refugees and vulnerable people due to conflicts were reported to be affected by sexual violence and abuse, increased drug use, lack of health infrastructure, education, income, and basic needs, and social structure breakdown [68].
Disease education/awareness programmes and community mobilisation/engagement campaigns were considered a necessary part of any plan to successfully prevent epidemics for the majority of the studied infectious diseases [9,10,18,26,28,31,49,50] Measures included education and sensitising programmes for infectious diseases targeting at-risk populations and populations in host communities [9] through culturally appropriate information on symptoms and how to seek medical advice and treatment [49].Disease awareness programmes for civilians [10,28,31], and importantly for military personnel [31] on personal protective measures, immunisations, chemoprophylaxis and surveillance were suggested.The distribution of public awareness material on proper personal hygiene, food, and water safety [19] for other infectious diseases was also suggested.In the case of HIV infection, the emphasis was placed on educating young people aged 15 to 24 [9] with the development of educational/awareness materials in appropriate languages [68], programmes for in-school and out-ofschool youth [68], peer education [68], youth centres [68], sports/drama groups [68], and programmes aimed at reducing teenage pregnancy and sexual violence [68].
Furthermore, investing and enabling health care and preventative services in locations that have been disrupted by conflict and in locations with displaced populations was stressed across the studied literature.The reconstruction and rehabilitation of health centres and hospitals [9,24] within conflict areas have been noted as a primary response strategy.Infection control procedures should also be instituted in healthcare centers including the development of procedures in establishing an isolation facility, ensuring safe water, sanitation and waste disposal and providing personal protective equipment for staff within hospitals [2].The provision of therapeutic and diagnostic supplies and testing equipment [28] and preparing with medications, and equipment standard medical facilities with intensive care capacity [31] have also been noted as key response measures, including the importance and need to adapt strategies, guidelines and tools [26], such as treatment regimens [32] and the expansion of user-friendly short-course DOTS for TB [32] in conflict settings.
The recruitment of health staff and the establishment of early disease detection training programmes for healthcare professionals are also critical measures to maintaining healthcare in conflict situations and in postconflict rehabilitation [27,28,32,33,43,49].Similarly, improved preparedness of the public health authorities for surveillance (including public health laboratories at central and regional levels) and response systems [19] is also essential.
For the vaccine preventable diseases identified within the context of this review, the studies suggested the implementation of several approaches towards vaccination strategies [13,27,37,39,41,44,51], aimed to cover at-risk populations both within combat areas and amongst displaced populations with vaccination at entry and exit screenings [39].Studies also described numerous approaches towards implementing vaccination of at-risk populations such as displaced persons, including organising vaccination campaigns at fixed posts where the team was based at the health facilities and at temporary post located at strategic areas such as transit points, bus stations and refuge sites [29,51,52], as well as the use of mobile outreach teams [51].In addition, the creation and use of medical supplies and global vaccine stockpiles were suggested as mitigation measures that could be available for rapid deployment in emergency and outbreak situations [16,19].In some cases, this is easily achievable, as with the provision of OCVs [15,20,24] while in other circumstances protocols including the maintenance of a cold chain for transport and the use of trained teams are needed [39].In all cases, encouraging the community to participate at every level of the vaccine rollout improves public trust which is essential for the effective implementation of vaccine rollout plans [29,[38][39][40].
The importance of collaborative efforts between international agencies and nongovernmental organisations, national and regional authorities and local/front-line NGOs was stressed in most of the studied articles [30, 38-40, 43, 44, 49, 51, 57, 59].During active conflicts, interoperability and biosurveillance information sharing across agencies are needed [30].In order to maintain the delivery and utilisation of health care in areas affected by armed conflicts, it was advised that local, national, regional, and international authorities cooperate [57].It was further recommended that international financial and logistical support should be given to front-line NGOs to reach and safely provide healthcare to isolated/hard-to-reach populations [43].Also, international organisations providing health services should be given unconditional safe access to conflict zones.Finally, political commitment is necessary to achieve as far as possible uninterrupted and safe medical and humanitarian aid to conflict zones [32,44], as well as support for post-conflict recovery.
Extended wars and conflicts often make people reliant on foreign aid.This need for international aid often lasts for a long time even after peace is restored.Therefore multi-agency humanitarian assistance must promote effective, efficient, and socio-culturally suitable healthcare in a sustainable way [69].It is of critical importance to improve the quality of life to avoid and minimise disease occurrence among both displaced and conflictaffected population's [70].As such, international organisations that provide health and humanitarian services should be given unconditional access to conflict zones [32] and should be allowed to function impartially within conflict [43].The government and opposition groups must be engaged with to ease passage of aid and access to conflict-affected populations [71].
Last but not least, studies have noted the importance of a proactive identification of vulnerabilities and locations for interventions through surveillance [14,19,31,38,43,46,50,51,58,62].It is essential to improve the preparedness of the public health authorities by increasing international surveillance [14,19,31,38,43,46,50,51,58,62] and international financial and logistical support for vaccine and immunisation of the population, especially in conflict-torn countries [43].Improved methods for measuring population movement within and between countries during complex emergencies are needed [20], through multisource surveillance techniques [20] and through the development of predictive tools to identify vulnerabilities and settings posing a high a risk of infectious disease [16].While advanced surveillance systems (i.e.genomics) are important, easy applicable early warning systems, such as tally sheets to monitor campaign coverage [51], are also beneficial.To this extent, tracking spatiotemporal patterns of populations and disease transmission [14], along with the early detection of outbreaks supporting the prediction of areas at increased risk for infectious disease introductions/outbreaks is essential.Surveillance and broad testing policies, not only for severe hospitalised cases but also for milder, asymptomatic cases are necessary response measures that could contribute to lower mortality [30].Furthermore, the creation of effective and targeted public health emergency response plans based on the acquired information is also needed to enable timely and effective mitigation of future health challenges arising in conflict-affected countries and in countries hosting displaced populations.

Strengths and limitations
The systematic investigation of the literature, the thorough assessment, data extraction, quality appraisal, and synthesis of published evidence are strengths of the current review.However, it is important to acknowledge certain limitations.This review focused on peer-reviewed evidence available in the English language.Therefore, relevant information published in other languages may be missing.Additionally, our inclusion criteria did not impose geographical restrictions, necessitating cautious interpretation of the findings in light of documented variations across countries and different disease outbreaks.Furthermore, while this review elucidates several factors contributing to infectious disease outbreaks in conflict settings, it is conceivable that not all causal pathways linking conflicts and infectious diseases were identified, as monitoring and assessing all pathways within conflict zones can pose significant challenges.Hence, future research endeavours should aim to shed further light on additional disease-specific pathways that precipitate outbreaks.The identification of qualitative information from key informants and/or patients within conflict zones could enhance our understanding of the issue.Future studies should consider addressing this aspect.In addition, incorporating econometric analyses would be interesting to indicate the impact of conflict on infectious diseases in economic terms.

Conclusion
Conflicts play a direct and indirect role in the transmission and propagation of infectious diseases due to population displacement, overcrowded settlements with poor sanitary conditions, disruption of infrastructure, reduction in functioning healthcare system, shortages of food, limited access to clean drinking water, medications and healthcare, delays in diagnosis and disruptions in vaccine coverage.The most important prevention and preparedness strategies for an infectious disease outbreak in a conflict situation included education/awareness campaigns, reconstruction of healthcare facilities including recruitment and training of healthcare workers, strengthening surveillance and early warning systems, enabling access to healthcare in conflict zones, deployment of global vaccine and medical stockpiles, and implementation of water-sanitation-hygiene interventions.Finally, collaboration between humanitarian and health actors, community engagement, and political will were identified as critical factors in responding to infectious disease outbreaks in conflict settings.Through identifying commonly reported risk pathways as well as mitigation strategies, the findings of this review may assist decisionmakers to implement evidence-based preparedness and response strategies for the timely and effective mitigation of future infectious disease outbreaks in conflict areas.
Abbreviations: ETCs = Ebola treatment centers, UN = United Nations, US = United States, WHO = World Health Organisation

Table 2
Impact of conflict on Cholera outbreaks

Table 3
Impact of conflict on COVID-19 outbreaks staff

Table 4
Impact of conflict on Tuberculosis outbreaks

Population Conflict to Disease Pathways Prevention and Preparedness Strategies Suggested/Implemented
Foreign health workers, nongovernmental organisations, and UN agencies had been leading an energetic international Ebola epidemic response, alongside local personnel who offered experience and linguistic and cultural awareness • World Bank dispatched financing, while US-supported vaccines, therapies, and laboratory/epidemiology capacity-building were proved essential Suggested:• Responders need greater capacity in surveillance, data analysis, laboratories, and clinical response, particularly experienced personnel to work with local leaders to build community trust and communication.•Increased security and ensuring safe humanitarian operations • The UN Security Council should mobilize high-level political attention and resources for the Ebola response • External partners should develop a plan to deploy public health personnel such regions • There should be an increase in funding to enhance local response capabilities • A transparent framework for responding to epidemics in conflict zones should be developed • Sustainable funding for national action plans for health security and a plan to safeguard public health action in conflict zones should be created

Table 5
Impact of conflict on Ebola outbreaks

Table 7
Impact of conflict on Malaria, Leishmaniasis, Measles, Dengue, Diphtheria and ABM outbreaks • The re-establishment of holding camps and vaccination posts at all entry points into IDP camps and host communities to ensure all new entrants are screened and vaccinated with